1. Field of the Invention
The present invention relates to a single strut mounted or boom mounted pressure measuring probe which provides multiple pressure readings to obtain necessary aircraft performance data across a wide range of angles of attack.
2. Prior Art
The advantages of having aerodynamically compensated static pressure sensing probes as well as incorporating pitot sensing and dual static systems in the same probe have been known. Various devices which provide satisfactory results in many conditions have been advanced. For example, an aerodynamically compensated dual static probe is shown as U.S. Pat. No. 3,482,445. In that patent the probe is provided with discontinuity or surface irregularity which causes an alteration of measured static pressure, thereby compensating for other defects such as adjacent portions of the fuselage so that dual compensating static sensing can be achieved by proper location of a pair of ports on the probe.
In many applications, it is necessary to measure local angle of attack on or ahead of the aircraft fuselage. In some prior devices, a set of pressure ports are generally made on the forward extremity of the probe so that the pressures sensed at these ports will vary in a known relationship; from such variation, the local angle of attack can be determined. For example, a pressure sensing instrument for aircraft flow angle is described under U.S. Pat. No. 3,318,146. This device discloses a combination of ports on a hemispherical shape subtending to a cylinder where a minimum of 3 and a maximum of 5 pressure ports are installed. The angle of attack is determined from a ratio (p.sub.1 -p.sub.2)/(p.sub.t -p.sub.4).
Both the above stated pitot-static tubes and angle of attack sensors have been extensively used in the past, but generally each unit is installed at different locations; thereby adding to the weight, drag, cost, as well as the complexity of the installation. A pressure sensor for determining altitude, airspeed, and angle of attack is shown in the U.S. Pat. No. 4,096,744. In this device, the functions of measuring pitot pressure, static pressure, and angle of attack pressures, are combined into a single unit. Angle of attack, using the device, may be determined by using a specific pressure ratio described in that patent and is very useful. However, the device disclosed herein provides increased sensitivity at angles of attack above 25.degree. or so and thus in advanced aircraft which do operate at angles of attack well above 40.degree., the increased sensitivity is a positive factor.